Research on Precise Desulfurization Technology for Blast Furnace Gas

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1. Technical background: In the field of steel metallurgy, during the blast furnace iron-making process, a combustible gas with low calorific value is produced as a by-product – blast furnace gas. Given the large volume of this gas, its recovery and effective utilization offer significant economic and environmental benefits； However, blast furnace gas contains harmful substances such as dust, chlorine, and sulfur, and it must undergo comprehensive purification before it can be utilized. Currently, the utilization of blast furnace gas mainly involves removing particulate matter through gravity separation and bag filtration. After that, following TRT-based pressure recovery power generation, the gas is supplied to various decentralized user units—such as blast furnace hot stoves, steel rolling reheating furnaces, and gas-fired power generators—for use as fuel. However, harmful substances such as sulfur and chlorine contained in blast furnace gas remain untreated. With the advancement of policies aimed at achieving ultra-low emissions in the steel industry, this sector has officially entered an era of ultra-low emissions; various users such as blast furnace hot blast stoves, rolling mill heating furnaces, and gas-fired power generation units are now required to keep the SO2 levels in their combustion exhausts within ultra-low emission limits. Currently, the treatment of blast furnace gas after combustion relies mainly on end-point treatment methods, requiring desulfurization facilities to be installed at multiple locations ； The existing blast furnace gas purification processes face significant challenges such as numerous and widespread emission sources, secondary pollution, an increase in exhaust gas volume after combustion, the need for larger treatment facilities, higher investment costs, repeated investments, and difficulties in management – issues that prevent them from meeting the requirements for SO2 control. Since 2016, Changchun Dongshi Technology (Group) Co., Ltd. has invested substantial human and financial resources in collaborating with relevant universities and research institutions to develop a new advanced desulfurization process for blast furnace gas, addressing the significant purification challenges associated with its use. The core technology of this process integrates blast furnace gas pretreatment technology + organic sulfur conversion technology + wet oxidation desulfurization technology ； Furthermore, a source-control approach for the total sulfur content in blast furnace gas is adopted, with advanced desulfurization processes being implemented to reduce the sulfur level in this gas, thereby ensuring that the SO2 levels in the exhaust gases generated by its combustion meet ultra-low emission standards ； It can also reduce the pressure on end-of-pipe treatment, and even eliminate the need for such treatment facilities. 2. Process overview: Specific process route – blast furnace gas pretreatment + organic sulfur conversion + wet oxidation desulfurization. After passing through a bag filter, blast furnace gas takes advantage of its relatively high pressure and temperature conditions (temperature ranging from 100–180°C and pressure at around 200 kPa). A pretreatment unit is then installed for the gas; targeted treatment techniques are employed to effectively remove impurities such as dust, oil, heavy metals, and inorganic chlorine from it ； Thereafter, an organic sulfur conversion unit is installed; the water vapor present in the blast furnace gas reacts with organic sulfur to produce H2S, thereby completing the conversion of organic sulfur. After that, the blast furnace gas is sent to a waste pressure power generation unit (TRT) ； After being cooled and depressurized by a TRT, the blast furnace gas has a temperature of around 40–80°C and a pressure of approximately 10–20 KPa ； A wet oxidation desulfurization unit is installed after the excess pressure recovery turbine (TRT) to remove H2S from the gas; the H2S level at the outlet is ≤20 mg/Nm3, or even below 10 mg/Nm3. This unit also removes any remaining organic sulfur from the blast furnace gas, ensuring that the SO2 levels in the exhaust gases generated after the combustion of the blast furnace gas meet the required standards. 3. Technical features: (1) The pretreatment unit employs targeted treatment techniques to remove various impurities, effectively preventing catalyst contamination and poisoning ； And there is no waste liquid discharge ； (2) In view of the high levels of COS and H2S in blast furnace gas, an efficient catalytic conversion process is employed ； (3) The internal structure of the organic sulfur conversion reactor is advanced and rational; it features low resistance per reactor, which reduces the pressure drop across the reactor bed and improves the catalyst utilization rate. (4) Make full use of the hierarchical utilization of energy; by leveraging the temperature, water vapor content, and system pressure before the TRT, it is possible to avoid the problems associated with cooling and dehydration followed by reheating required for the conversion of organic sulfur after the TRT. This also allows for a reduction in the flow rate through the catalyst bed, thereby minimizing pressure drop losses and saving resources and energy. (5) The wet oxidation desulfurization unit features a salt-suppression design with high sulfur capacity, and utilizes proprietary patented technologies such as distributors, resistance-free nozzles, and rich-liquid sulfur precipitation reactors to reduce investment costs, operating expenses, and floor space requirements ； (6) The DSH high-sulfur-capacity salt-inhibiting catalyst has a salt-inhibiting effect; no by-products are formed during the desulfurization process, and no waste liquid is generated. (7) The entire desulfurization system converts organic sulfur and inorganic sulfur through transformation and absorption, ultimately turning them into elemental sulfur; it is equipped with a sulfur recovery unit that produces sulfur, which is sold as a by-product, with no solid waste generated. 4. Technical advantages: (1) High precision in preprocessing, which effectively ensures the long-term stable operation of the conversion agent ； (2) Organic sulfur converters possess sulfur-resistant conversion capabilities ； (3) The conversion rate of organic sulfur is high, exceeding 90%. ； (4) Wet desulfurization has high efficiency; it can remove residual organic sulfur as well, and it is capable of reducing H2S levels in gas to below 10 mg/Nm3 ； (5) The device occupies little space and requires low investment; it boasts high operational stability and reliability ； The device has low operating costs and low maintenance expenses ； (6) High degree of automation: The designed desulfurization unit for blast furnace gas features highly automated control, allowing for one-button startup via computer. 5. Conclusion: Against the backdrop of \"ultra-low emissions\" in the steel industry, desulfurization of blast furnace gas is essential; implementing advanced desulfurization of blast furnace gas can significantly reduce the overall SO2 emissions from the steel industry. The blast furnace gas deep desulfurization process technology independently developed by our company features significant advantages such as reliable operation, low resistance and high efficiency, mature technology, and stable performance ； It can be selected and used directly. Our company can provide a complete set of process design packages for blast furnace gas desulfurization, as well as overall engineering design, renovation services for desulfurization systems, core equipment and various catalysts. We also offer start-up support and after-sales services.